Image formation is a procedure whereby a digital image is recreated on a medium by propelling droplets of ink or another type of print fluid onto a medium, such as paper, plastic, a substrate for 3D printing, etc. Image formation is commonly employed in apparatuses, such as printers (e.g., inkjet printer), facsimile machines, copying machines, plotting machines, multifunction peripherals, etc. The core of a typical jetting apparatus or image forming apparatus is one or more liquid-droplet ejection heads (referred to generally herein as “printheads”) having nozzles that discharge liquid droplets, a mechanism for moving the printhead and/or the medium in relation to one another, and a controller that controls how liquid is discharged from the individual nozzles of the printhead onto the medium in the form of pixels.
A typical printhead includes a plurality of nozzles aligned in one or more rows along a discharge surface of the printhead. Each nozzle is part of a “jetting channel”, which includes the nozzle, a pressure chamber, and a mechanism for ejecting the print fluid from the pressure chamber and through the nozzle, which is typically a diaphragm that is driven by an actuator (e.g., a piezoelectric actuator). A printhead also includes a drive circuit that controls when each individual jetting channel fires based on image data. To jet from a jetting channel, the drive circuit provides a jetting pulse to the actuator, which causes the actuator to deform a wall of the pressure chamber via the diaphragm. The deformation of the pressure chamber creates pressure waves within the pressure chamber that eject a droplet of print fluid (e.g., ink) out of the nozzle. A drop emerging from the nozzle will extrude as a jet which necks down and breaks off from the print fluid remaining in the nozzle. In an ideal case, the jet will move towards the medium with surface tension forces pulling the liquid into a spherical droplet. The surface tension will also cause the print fluid still attached to the nozzle to be drawn back into the nozzle. After the initial break-off, the jet has a head containing most of the print fluid, and a ligament or tail that extends from the head. When detached, the ligament will start to merge into the head of the jet. Depending on the viscosity of the print fluid, jetting velocity, and other jetting characteristics, the ligament may not merge into the head before it reached the medium, which results in satellites that are undesirable.